关键词: 机械推力矢量, 襟翼偏转, 流动控制, 流动显示, 射流分离与附壁

Abstract: Traditional mechanical thrust vectoring nozzles feature complex structures and large jet deflection angles, whereas fluidic thrust vectoring nozzles possess simple structures but suffer from small jet deflection angles, as well as hysteresis and sudden jump phenomena during vectoring angle control. In this paper, a two-dimensional jet control device deflected by a movable Coanda wall is proposed, which utilizes movable walls of different lengths to induce large-angle jet deflection. Through experimental research on the variation laws of force vector angles and flow structures, the deflection control characteristics of the jet under different ratios of wall length to jet exit height (K) are presented. Additionally, combined with schlieren flow visualization technology, the deflection characteristics of the jet at high speeds under different nozzle pressure ratios (NPR) are obtained.Experimental results indicate that during the deflecting and returning processes of the movable wall, the jet consistently experiences three states: wall attachment, unstable fluctuation, and wall detachment. The wall length affects the maximum deflection angles during jet detachment and attachment. When K = 20, there is a 3° hysteresis, and the jet can reach a maximum deflection angle of 56°. As the K value decreases, the hysteresis gradually disappears. When K = 5, no hysteresis occurs, and the jet can achieve a deflection angle of 42°. Under high-speed conditions with NPR = 4.5, the wall-induced jet can still achieve a deflection angle of 31°.

Key words: mechanical thrust vectoring, flap deflection control, active flow control, flow visualization, jet separation &, reattachment